Microbial oil, production method for microbial oil, concentrated microbial oil, and production method for concentrated microbial oil

Abstract

A microbial oil comprising: a specific amount of at least one polyunsaturated fatty acid having at least 20 carbon atoms in fatty acid alkyl ester form and/or in free fatty acid form; and specific amount of thermally-produced fatty acid having from 16 to 22 carbon atoms in a fatty acid alkyl ester form and/or a free fatty acid form. A production method thereof comprising: providing a starting oil containing at least one polyunsaturated fatty acid having at least 20 carbon atoms in an alkyl ester form and/or a free fatty acid form obtained from microbial biomass; performing a rectification of the starting oil under specific conditions; and obtaining the aforementioned microbial oil. A concentrated microbial oil obtained using the production method described above, and a production method thereof. An agent for treating or preventing an inflammatory disease comprising the microbial oil or the concentrated microbial oil.

The invention claimed is: 
     
       1. A microbial oil comprising:
 dihomo-γ-linolenic acid (DGLA) in a fatty acid alkyl ester form or in a free fatty acid form at a content of at least 50% by weight of the total weight of fatty acids in the microbial oil; and 
 one or more trans isomers of DGLA at a total content of 0.0001% to 3.0% by weight of the total weight of fatty acids in the microbial oil, 
 wherein the microbial oil comprises a mixture of fatty acid alkyl esters or free fatty acids obtained by the steps of i) performing hydrolysis or alkyl esterification of a crude oil obtained from a microbial biomass from a microorganism capable of producing DGLA to produce a hydrolyzed or esterified crude oil; and ii) purifying the hydrolyzed or esterified crude oil by rectification using a distillation column containing a structured packing, under conditions including a column bottom temperature of 160° C. to 230° C. and a minimum pressure in a distillation column of 0.1 Pa to 30 Pa, 
 wherein the one or more trans isomers of DGLA are generated during the rectification step as thermally-produced fatty acids. 
 
     
     
       2. The microbial oil according to  claim 1 , wherein the content of DGLA is 80% to 98% by weight of the total weight of fatty acids in the microbial oil. 
     
     
       3. The microbial oil according to  claim 1 , wherein the total content of the one or more trans isomers of DGLA is 0.001% to 3.0% by weight of the total weight of fatty acids in the microbial oil. 
     
     
       4. The microbial oil according to  claim 1 , further comprising a saturated fatty acid having 22 or 24 carbon atoms, wherein the total content of the saturated fatty acid having 22 carbon atoms and the saturated fatty acid having 24 carbon atoms is i) at most 6.0% by weight of the total weight of fatty acids in the microbial oil, or ii) at most 10/100 (weight ratio) of the content of DGLA. 
     
     
       5. The microbial oil according to  claim 1 , further comprising a saturated fatty acid having 24 carbon atoms, wherein the content of the saturated fatty acid having 24 carbon atoms is i) at most 3.0% by weight of the total weight of fatty acids in the microbial oil, or ii) at most 4/100 (weight ratio) of the content of DGLA. 
     
     
       6. The microbial oil according to  claim 1 , further comprising one or more fatty acids having a partition number of 12 to 16 and having a number of carbon atoms other than 20, wherein the content of the one or more fatty acids having a partition number of 12 to 16 and having a number of carbon atoms other than 20 is i) at most 10.0% by weight of the total weight of fatty acids in the microbial oil, or ii) at most 15/100 (weight ratio) of the content of DGLA. 
     
     
       7. The microbial oil according to  claim 6 , wherein the one or more fatty acids having a partition number in the range of 12 to 16 and having a number of carbon atoms other than 20 are selected from the group consisting of a saturated fatty acid having 18 carbon atoms, a monounsaturated fatty acid having 18 carbon atoms, a diunsaturated fatty acid having 18 carbon atoms, a triunsaturated fatty acid having 18 carbon atoms, and a tetraunsaturated fatty acid having 18 carbon atoms. 
     
     
       8. The microbial oil according to  claim 1 , wherein the one or more trans isomers of DGLA comprise i) a first substance, an ethyl ester of which has a relative retention time with a peak appearing within a range of from 1.001 to 1.011 or ii) a second substance, an ethyl ester of which has a relative retention time with a peak appearing within a range of from 1.013 to 1.027 in a gas chromatography analysis, wherein the relative retention time of ethyl dihomo-γ-linolenate is defined as 1 in the gas chromatography analysis performed under the following conditions:
 Device: 6890N Network GC system (Agilent Technologies); 
 Column: DB-WAX, length 30 m×inside diameter 0.25 mm×film thickness 0.25 μm (Agilent Technologies); 
 Column temperature conditions: 2.5 minutes at 60° C.→heated at 20° C./min→180° C.→heated at 2° C./min→15 minutes at 230° C.; 
 Inlet temperature conditions: 210° C., splitless, split vent sampling time 1.5 min, purge flow rate 40 mL/min; 
 Injection conditions: injection volume 1 μL, sample concentration 1 mg/mL or less Detector: FID; 
 Detector temperature: 280° C.; and 
 Carrier gas conditions: helium, linear velocity 24 cm/min. 
 
     
     
       9. The microbial oil according to  claim 8 , wherein the total content of the first substance and the second substance is 0.001% to 2.8% by weight of the total weight of fatty acids in the microbial oil. 
     
     
       10. The microbial oil according to  claim 7 , wherein the content of the monounsaturated fatty acid having 18 carbon atoms is i) at most 7.0% by weight of the total weight of fatty acids in the microbial oil, or ii) at most 10/100 (weight ratio) of the content of DGLA. 
     
     
       11. The microbial oil according to  claim 7 , wherein the content of the diunsaturated fatty acid having 18 carbon atoms is at most 7/100 (weight ratio) of the content of DGLA. 
     
     
       12. The microbial oil according to  claim 7 , wherein the total content of the monounsaturated fatty acid having 18 carbon atoms and the diunsaturated fatty acid having 18 carbon atoms is at most 15/100 (weight ratio) of the content of DGLA. 
     
     
       13. The microbial oil according to  claim 7 , wherein the content of the saturated fatty acid having 18 carbon atoms is at most 11/100 (weight ratio) of the content of DGLA. 
     
     
       14. A production method for obtaining the microbial oil according to  claim 1 , comprising the steps of:
 (a) providing a starting oil containing DGLA in an alkyl ester form or in a free fatty acid form, obtained from a microbial biomass from a microorganism capable of producing DGLA; and 
 (b) (i) purifying the starting oil by rectification under conditions including a column bottom temperature of 160° C. to 230° C. and a minimum pressure in a distillation column of 0.1 Pa to 30 Pa, thereby obtaining the microbial oil; or
 (ii) performing rectification on the starting oil using a distillation column containing a structured packing under conditions including a column bottom temperature of 160° C. to 230° C. and a minimum pressure in the distillation column of 0.1 Pa to 30 Pa, 
 
 thereby obtaining the microbial oil. 
 
     
     
       15. The production method according to  claim 14 , wherein step (b) comprises a plurality of rectification cycles under mutually differing conditions for the column bottom temperature and the minimum pressure in the distillation column. 
     
     
       16. The production method according to  claim 15 , wherein the rectification step comprises a low-temperature rectification at a column bottom temperature of 160° C. to 220° C. and a minimum pressure in the distillation column of 0.1 Pa to 30 Pa; and a high-temperature rectification at a column bottom temperature of 170° C. to 230° C. and a minimum pressure in the distillation column of 0.1 Pa to 30 Pa, and wherein the column bottom temperature in the high-temperature rectification is 3° C. to 20° C. higher than the column bottom temperature of the low-temperature rectification. 
     
     
       17. The production method according to  claim 14 , wherein the structured packing of step (b) (ii) has a specific surface area per unit of 125 m 2 /m 3  to 1700 m 2 /m 3 . 
     
     
       18. The microbial oil of  claim 1 , wherein the microbial oil is a concentrated microbial oil, comprising:
 a content of DGLA, in a fatty acid alkyl ester form or in a free fatty acid form, of 90% to 98% by weight of the total weight of fatty acids in the concentrated microbial oil; 
 a total content of a saturated fatty acid having 24 carbon atoms and a saturated fatty acid having 22 carbon atoms of at most 1.0% by weight of the total weight of fatty acids in the concentrated oil; and 
 a content of a monounsaturated fatty acid having 18 carbon atoms of at most 5.0% by weight of the total weight of fatty acids in the concentrated oil. 
 
     
     
       19. A production method for obtaining a concentrated microbial oil, comprising:
 obtaining a microbial oil containing DGLA in a fatty acid alkyl ester form or in a free fatty acid form using the production method according to  claim 14 ; and 
 concentrating the obtained microbial oil using reverse phase column chromatography, thereby obtaining the concentrated microbial oil. 
 
     
     
       20. A supplement, a medicament, a cosmetic, or an animal food, each comprising the microbial oil according to  claim 1 . 
     
     
       21. A supplement, a medicament, a cosmetic, or an animal food, each comprising the concentrated microbial oil obtained by the production method of  claim 19 . 
     
     
       22. A medicament comprising the microbial oil according to  claim 1 .